1. Field of the Invention
The present invention relates to a magnetic disk drive for vertical recording.
2. Description of the Related Art
In recent years, together with the progress of downsizing and increase in capacity of magnetic disk drive, refinement of magnetic particles in a medium is demanded. However, according to a conventional recording method which is called in-plane recording method, since refinement of magnetic particles makes a factor of thermal instability, it is difficult to produce very fine magnetic particles. Therefore, a vertical magnetic recording method which is superior in thermomagnetic relaxation and so forth is examined. In a common vertical magnetic recording method, a two-layer film medium is used which is formed by laminating a soft magnetic ground layer on a substrate and laminating a vertical magnetization film on the soft magnetic ground layer.
Referring to FIG. 1, there is illustrated a relationship between a conventional vertical recording magnetic head 2 and a vertical magnetic recording medium 8. The vertical magnetic recording medium 8 is formed by laminating a soft magnetic ground layer 12 of Ni—Fe or the like on a non-magnetic substrate 10 and laminating a vertical magnetization film 14 made of Co—Cr on the soft magnetic ground layer 12. The soft magnetic ground film 12 has a thickness of 1 μm or more, and the vertical magnetization film 14 has a thickness of 0.1 μm or less.
The vertical recording magnetic head 2 includes a leading pole 4 and a trailing pole 6, and most part of magnetic fluxes 16 outgoing from a tip end 4a of the leading pole 4 of the magnetic head 2 pass through the soft magnetic ground film 12 and return to the trailing pole 6. In this manner, in the vertical magnetic recording medium 8, since most part of the magnetic fluxes 16 pass through the soft magnetic ground film 12 having a great thickness and return to the trailing pole 6, a magnetic field in a steep vertical direction can be easily applied to the vertical magnetization film 14. Therefore, the gap length G to be defined between the tip end 4a of the leading pole 4 and a tip end 6a of the trailing pole 6 need not be set very short. Generally, the gap length G is set to a great gap length of approximately 10 μm. Generally, since the shape of the tip end 4a of the leading pole 4 and the tip end 6a of the trailing pole 6 is a rectangular shape, the magnetic fluxes 16 of a rectangular shape are applied to the vertical magnetic recording medium 8.
A conventional magnetic disk drive for which a vertical recording method is used has such problems as described below. When a head slider performs seeking movement to the inner or outer side of a magnetic disk, since the air bearing surface (ABS) shape or flotation face shape of the head slider is a rectangular shape, a yaw angle dependence occurs together with the rectangular shape of fluxes to be applied as described above. Then, upon data recording, data to be recorded is recorded protruding to a one-side track edge, and then upon reproduction, the reproduction signal quality is degraded by an influence of the protruding recorded portion. Conventionally, the flotation face shape of the head slider is set to an inverse trapezoidal shape or a rectangular shape having a taper on the upper side to decrease the protruding portion of the magnetic fluxes upon recording on the inner or outer side. However, it is very difficult from a viewpoint of a fabrication process to work the head slider into such a special shape as described above. Further, also the yield is low, and a considerable expense is required from a viewpoint of the cost.